Believing that a pile of debris from a military surveillance nuclear-testing device found in the New Mexico desert in 1947 was the wreckage of an extraterrestrial aircraft—well, it’s a plausible belief. You’d have to ignore a great deal of very persuasive disconfirming evidence and believe in an extremely large and extremely secretive government conspiracy, but, hey, a lot of people think along similar lines. Looking up at the night sky and seeing alien ships when others see Venus, unconventional aircraft, odd stellar formations, northern lights, blinking towers—or any other visual manifestations from a potpourri of earthly phenomena—hey, that’s not too strange. Some people have more imagination than others; they fill in the blanks where the rest of us stick pretty close to what their eyes tell them.

But alien abductions are another kettle of fish altogether. This is not a matter of perceiving ambiguous stimuli in a certain way or believing in conspiracies. And remember, some conspiracies do happen. But do alien abductions? Extraterrestrials kidnapping humans, taking them to their space ships, performing experiments on them, cutting them open, raping them, forcing women to bear hybrid babies? Thousands of people believe they have been abducted by aliens. Their memories of these experiences are vivid, painful, and terrifyingly real. What’s up here? Should we believe their stories?

Tales of alien contact have been narrated for centuries. Francis Godwin‘s The Man in the Moone (1638) and Ralph Morris’ A Narrative and the Life and AstonishingAdventures of John Daniel (1751), are taken today as intended fiction. However, in 1758, in Concerning Earths inOur Solar World, Emanuel Swedenborg made the claim that he had actually visited all the then-known planets, which he described in great detail, all inhabited by creatures who had devised ideal societies. We now know of the existence of planets that were not described by Swedenborg (Uranus, Neptune, and Pluto—the last of which astronomers have declassified as a planet), and we know the ones he described bear no relation to his accounts, and of course, all the evidence we have says they’re uninhabited. And how was Swedenborg to know that half the planets in the solar system were gaseous and can’t support the weight of solid objects, such as humans? Or that Venus is a toxic hothouse of sulphuric acid that could support no conceivable life whatsoever. The truth is, he knew virtually nothing about what was on our solar system’s planets—and he couldn’t have.

The pre-1947 literature on alien contact usually has the contactee visiting another planet. These narratives include an account given in 1890 by Helen Smith of Martians speaking a language that sounds very much like French; in 1906 by Sarah Weis, who described nonexistent Martian canals in great detail; in 1918 by Aleister Crowley, who describes contact with “Lam,” an inhabitant of a distant constellation who has a bulbous head and tiny, beady eyes; and in 1930 by one Willard Magoon, who described Mars as a beautiful, lush planet of forests, parks, and gardens.